Adhesion binders with glutarimide units

ABSTRACT

This invention provides an adhesion binder for binding fluorinated polymers, for example PVDF, with incompatible polymers such as polyamides. The binder is a polymer A which has glutarimide, acid, anhydric and acrylate units, and is useful for the production of fuel hoses. When mixed with a fluorinated polymer such as PVDF, copolymer A acts both as a binder and as a barrier.

TECHNICAL FIELD

The present invention relates to an adhesion binder containingglutarimide moieties and its application as a barrier material. Itrelates more particularly to the coextrusion with a layer or a film offluorinated polymer and especially of polyvinylidene fluoride (PVDF).

PRIOR ART

EP 3,449 describes the coextrusion of PVDF with polyurethanes (PU); itis not necessary to use a binder. FR 2,436,676 describes the coextrusionof PVDF with polymethyl methacrylate (PMMA) and apoly(acrylonitrile-butadiene-styrene) (ABS), the PMMA film being betweenthe PVDF and ABS films. Another example has been made with polyvinylchloride (PVC) in place of ABS. EP 450,994 describes an improvement tothe above technique, which uses as coextrusion binder the mixture:

27 to 50 parts of PMMA,

73 to 50 parts of a product itself consisting of 35 to 50 parts of PVDFper 100 parts, and

65 to 50 parts of acrylic or methacrylic elastomer.

This improvement increases the adherence of PVDF to ABS.

However, no coextrusion binder exists which is satisfactory for bondinga PVDF film to polyamide or to a product based on polyamide.

DESCRIPTION OF THE INVENTION

The Applicant has now found that a polymer A which contains thefollowing moieties: ##STR1## in which R₁ and R₂, which may be identicalor different, represent H or a linear or branched alkyl having from 1 to20 carbon atoms ##STR2## in which (i) R₄ and R₅, which may be identicalor different, represent H or a linear or branched alkyl having 1 to 20carbon atoms, (ii) R₃ represents H, an alkyl, cycloalkyl, aryl, alkaryl,aralkyl or a heterocycle ##STR3## in which R₆ represents H or a linearor branched alkyl having from 1 to 20 carbon atoms ##STR4## in which R₇represents H or a linear or branched alkyl having from 1 to 20 carbonsand R₈ represents a linear or branched alkyl having from 1 to 20 carbonatoms, is an adhesion binder for polyvinylidene fluoride (PVDF) whichallows it to adhere to polymers which are incompatible with it. PolymerA may for example be a derivative of PMMA. It may be obtained byreaction of PMMA with ammonia or amines. Other polymers A and theirpreparation processes are described in EP 216,505. The moieties 3advantageously represent less than 20% and preferably from 1 to 6% byweight of copolymer A.

Among the fluorinated polymers according to the invention, there may bementioned:

homo- and copolymers of vinylidene fluoride (VF2),

homo- and copolymers of trifluoroethylene (VF3)

homo- and copolymers, and especially terpolymers, combining the residuesof chlorotrifluoroethylene (CTFE), tetrafluoroethylene (TFE),hexafluoropropene (HFP) and/or ethylene moieties and optionally VF2and/or VF3 moieties. By way of example, there may be mentionedpolytetrafluoroethylene (PTFE) and poly(ethylene-tetrafluoroethylene)(ETFE).

Fluorinated polymer is also understood to refer to mixtures of at least70% by weight of the above with other polymers.

Among the fluorinated polymers, the homo- and copolymers of vinylidenefluoride possessing at least 70% by weight of VF2 residues, denotedthroughout the text by PVDF, are advantageously used. PVDF is alsounderstood to refer to the mixtures of the above with at least one otherthermoplastic polymer, on condition that at least 50% by weight of VF2moieties are present in the mixture.

Among the polymers which are incompatible with the fluorinated polymers,especially PVDF, there may for example be mentioned polyamides,copolyamides or polyamide alloys, on their own or as a mixture. By wayof example of polyamides (PA), PA-4,6, PA-6,6, PA-6, PA-6,12, PA-11,PA-12 and PA-12,12 or their mixtures may be mentioned. The polyamidealloys may be those consisting of a polyamide matrix in which aredispersed particles of another polymer, such as those described in theU.S. Pat. No. 4,174,358. The polyamides may contain plasticizers. Theinvention also relates to mixtures of polymer A with a polymer in orderto lower its modulus of elasticity. In fact, the binder consisting ofpolymer A is too rigid for certain applications; it is useful to mix itwith another polymer in order to render it less rigid. The amount ofthis polymer is chosen according to the desired rigidity. Fluorinatedpolymer modified by elastomers or a polymer which is compatible withpolymer A may be used. The binder according to the invention may be usedas coextrusion binder.

The invention also relates to the material containing three layers,namely a layer of PVDF, a layer of the binder according to the inventionand a layer of a polymer which is incompatible with the fluorinatedpolymer, successively. These layers may be plates or films; they may beplanar or cylindrical. They are for example pipes or tubes. The polymerwhich is incompatible with the fluorinated polymer is preferably apolyamide, a copolyamide or a polyamide alloy. This material containingthree layers may be prepared by the usual techniques of coextrusion orof duplicate moulding. The three-layer material may be prepared bydirect coextrusion or else, for example, the fluorinated polymer layermay be extruded, followed by a repeat extrusion or coextrusion of thelayer of binder and the incompatible polymer layer on the layer offluorinated polymer. It would not be departing from the scope of theinvention if the material contained other layers; for example, on thefluorinated polymer layer there could be a polyurethane layer, that isto say that it would be in the order PA/binder based on polymerA/fluorinated polymer/PU. There could also be another binder on thefluorinated polymer layer, for example that described in EP 450,994,followed by a layer of ABS, that is to say that it would be in the orderPA/binder based on polymer A/fluorinated polymer/binder/ABS. It is clearthat the binder of the invention could also be present several times,that is to say that it would be in the order PA/binder based on polymerA/fluorinated polymer/binder based on polymer A/PA. A particularlyadvantageous form of this material is a tube whose outer layer is madeof polyamide and whose inner layer is made of fluorinated polymer, andpreferably of PVDF. This tube is useful for the supply of fuel toautomobile engines.

For reasons of safety and of environmental protection automobilemanufacturers impose mechanical characteristics on the fuel pipes:strength and flexibility, and characteristics of increased resistance topermeability. The pipes must be of the lowest possible permeability topetroleum products and to their additives, in particular to methanol.

Currently, polyamide pipes are commonly used in the automobile industry.Polyamides represent an ideal material for this pipe application, theirmechanical strength being excellent and their flexibility beingsufficient for a pipe to withstand the accumulation of flexion movementswithout breaking for virtually the entire lifetime of a vehicle. Thesepipes made of polyamide no longer meet the new demands of automobilemanufacturers regarding permeability. With the increasing presence ofmethanol in petrol, the sensitivity of the pipes made of polyamide isrevealed by a swelling of the pipe, resulting in a decrease in themechanical properties, and in size modifications.

In order to overcome this disadvantage, while at the same time retainingthe mechanical effects of polyamides, the subject of the inventionconsists in lining the inner wall of the polyamide pipe with a layer offluorinated polymer, preferably of PVDF. The layer of fluorinatedpolymer is preferably as thin as possible in order to retain the maximumflexibility of the polyamide, given that fluorinated polymers, andespecially PVDF, are not particularly reputed for their properties ofsuppleness.

It is recommended that, with the polyamide-based fuel supply pipes forengines generally having an outside diameter of 6 to 12 mm, thethickness of the inner layer of fluorinated polymer, preferably PVDF, isbetween 10 μm and 1 mm and that of the polyamide between 0.8 and 1.8 mm,the pipe being completed by an intermediary adhesion binder layerbetween the polyamide and the fluorinated polymer of 10 μm to 1 mm.

It is essential that the fluorinated polymer is efficiently bonded tothe polyamide. A pipe which has no bonding between the fluorinatedpolymer and the polyamide cannot have a good flexibility and,consequently, cannot be easily folded or bent by hot forming; in thiscase, the thinnest material forms folds during the operation.

Moreover, if the two layers are not mutually bonded, the possiblecondensation of gases between the two layers may result in deformationof the thinnest part of the pipe with time. In addition, as the pipesare connected to one another, as well as to the fuel tank and to thecarburettor, by pipe couplings, the latter cannot provide theleakproofing if they bear upon two dissociated layers. Finally, in thecase where the thickness of the fluorinated polymer layer inside thetube is very thin, for example from 10 to a few tens of μm, and withoutahesion, a pressure drop in the pipe irreversibly deforms thefluorinated polymer film, rendering the pipe unusable.

It is observed that such a tube consisting of an inner layer offluorinated polymer bonded by the adhesion binder according to theinvention to an outer layer of polyamide makes it possible to decreasethe permeability by a factor of 10 relative to that of an equivalentpipe made of polyamide, while at the same time retaining the otherproperties, such as the cold impact strength, within the limits of theautomobile manufacturers' specification sheets.

According to another form of the invention, the fuel pipe may be formedfrom a central layer of fluorinated polymer, preferably PVDF, with, oneither side, a layer of the binder of the invention and a layer ofpolyamide, that is to say that the pipe has 5 layers: PA/binder based onpolymer A/fluorinated polymer/binder based on polymer A/PA.

It would not be departing from the scope of the invention if thepolyamide layer(s) comprised or essentially consisted of reground pipes,that is to say batches of pipes based on polyamide, and especiallymultilayer structures according to the invention, which are ground andoptionally mixed with the polyamide. These regrinds may also be placedin an intermediate layer between the binder and the PA.

For fuel pipes, the binder based on polymer A is preferably mixed withfluorinated polymer and/or fluorinated polymer which is modified by anelastomer or plasticized, and optionally an elastomer which iscompatible with A, as mentioned above, in order to render it less rigid.When a multilayer structure is produced according to the invention, inwhich the binder based on polymer A also contains fluorinated polymer,it is preferable that the fluorinated polymer present in the binder isthe same as that which is found in the adjacent layer of fluorinatedpolymer.

The binder may consist of at least 10% by weight of polymer A, theremainder being fluorinated polymer, preferably PVDF, and an impactmodifier. Success has been gained with the use of formulas containing(in % by weight):

12 to 20% of polymer A,

30 to 60% of PVDF,

20 to 40% of MBS elastomer, the total being 100%.

MBS denotes impact modifiers which take the form of particles having acore made of styrene/butadiene rubber and a shell made ofacrylic/styrene.

The fuel pipes thus manufactured have an exceptional resistance toalcohols, to alcohol-containing fuels and to heat.

The Applicant has also discovered that mixtures of polymer A andfluorinated polymer were adhesion binders and, simultaneously, barriermaterials towards fuel, in particular alcohol-containing fuel. Fuelpipes consisting of a layer of this binder between two layers ofpolyamide may also be obtained; in place of fluorinated polymer it isadvantageously possible to use fluorinated polymer modified byelastomers or to add fluorinated polymer which has been thus modifiedand/or a polymer which is compatible with polymer A to the binder base(polymer A and fluorinated polymer).

WAYS OF PERFORMING THE INVENTION

The examples which follow illustrate the invention without, however,limiting it.

In these examples, the polymers which are incompatible with thefluorinated polymers (homo- and copolymer of VF2) are polyamides.

The composites PVDF/binder/PA are pipes, but could be films, tanks orreservoirs.

These pipes are produced by coextrusion.

This technology is described in numerous scientific works (for examplein "Plastics Extrusion Technology", edited by F. Hensen, 1988, 738pages, ISBN: 0-19-520760-2). The coextrusion line used makes it possibleto produce pipes containing either 1, 2, 3, 4 or 5 layers. The pipesproduced are calibrated to the following dimensions: outside diameter 8mm and internal diameter 6 mm.

The standard used for assessing the resilience of the pipes is thestandard DIN 53453. The tests are conducted at -40° C.

The permeability tests are conducted according to the "micro SEED test"method by recirculation of the test fuel in the pipes. The test fuelsare:

M15, mixture of methanol (15%), isooctane (42.5%) and toluene (42.5%) byvolume. In this case, the recirculation is performed at 50° C. at apressure of 4 bar.

TF1, mixture of ethanol (9%), isooctane (45.5%) and toluene (45.5%) byvolume. In this case, the recirculation is performed at 40° C. at apressure of 2 bar.

The stripping tests on tubes (adhesion between the layers of themultilayer structure) are carried out on a dynamometer at a rate of 200mm/min and for a stripping angle of 180°. The adhesion is measured ing/cm. The following correspondence is used:

    ______________________________________                                        Interfacial Adhesion > 10,000 g/cm                                                                     ++++                                                 (Undelaminable Structure)                                                     6000 g/cm < Interfacial Adhesion < 10,000 g/cm                                                         +++                                                  2000 g/cm < Interfacial Adhesion < 6000 g/cm                                                           ++                                                   Interfacial Adhesion < 2000 g/cm                                                                       0                                                    ______________________________________                                    

EXAMPLES

                  TABLE 1                                                         ______________________________________                                        Monolayer pipes made of polyamide; this constitutes the reference.                     Permeability                                                                            Permeability                                                                            DIN                                                       M15       TFI  sic! Impact                                                    (g/m.sup.2 /24 h)                                                                       (g/m.sup.2 /24 h)                                                                       at -40° C.                                ______________________________________                                        Polyamide #1           69.7      0 C/10                                       Polyamide #2                                                                             420         137.0     0 C/10                                       ______________________________________                                    

Polyamide #1 is a PA-12 plasticized with 7.5% by mass ofn-butylbenzenesulphonamide (BBSA), displaying a flexural modulus of 450MPa (Standard ISO 178) and a notched Charpy impact strength of 9 kJ/m²at -40° C. (Standard ISO 179).

Polyamide #2 is a PA-11 plasticized with 13% by mass of BBSA, displayinga flexural modulus of 350 MPa (Standard ISO 178).

0 C/10=no breakages over 10 tests according to the standard.

                  TABLE 1 bis                                                     ______________________________________                                        Monolayer pipe made of PVDF                                                             DIN Impact at -40° C.                                        ______________________________________                                        PVDF #1     10 C/10                                                           ______________________________________                                    

PVDF #1 is a homopolymer of fluidity 13 g/10 min at 230° C. under 5 kg(Standard ISO 1133).

This example illustrates the low strength of PVDF with respect to PA.

                  TABLE 2                                                         ______________________________________                                        Multilayer pipes with an inner layer of PVDF.                                                     Permeability                                                                            Permeability                                                                          DIN                                          Structure of   M15       TFI  sic!                                                                             Impact                                  Ex.  the Pipe       (g/m.sup.2 /24 h)                                                                       (g/m.sup.2 /24 h)                                                                     at -40° C.                       ______________________________________                                        1    Polyamide #2/Binder                                                                          30        1.4     0 C/10                                       #1/PVDF #1                                                                    (700 μm/80 μm/220 μm)                                           2    Polyamide #2/Binder #1/  2.6     0 C/10                                       PVDF #1                                                                       (820 μm/60 μm/120 μm)                                           3    Polyamide #2/Binder #1/  3.8     0 C/10                                       PVDF #3                                                                       (750 μm/50 μm/150 μm)                                           4    Polyamide #2/Binder #2/  8.3     0 C/10                                       Polyamide #1                                                                  (700 μm/100 μm/250 μm)                                          5    Polyamide #1/Binder #3/                                                                      70        5.7     0 C/10                                       Polyamide #1                                                                  (410 μm/150 μm/410 μm)                                          6    Polyamide #1/Reground    3.0     0 C/10                                       Material/Binder #1/                                                           PVDF#2                                                                        (380 μm/380 μm/80 μm/                                                150 μm)                                                               7    Polyamide #2/Binder #1/  3.2     0 C/10                                       PVDF #1/PVDF #3                                                               (750 μm/50 μm/100 μm/                                                50 μm)                                                                8    Polyamide #1/Binder #1/  <5      0 C/10                                       PVDF #2/Binder #1/                                                            Polyamide #1                                                                  (380 μm/65 μm/100 μm/                                                65 μm/380 μm)                                                      ______________________________________                                    

PVDF #2 is a homopolymer of fluidity 8 g/10 min at 230° C. under 5 kg(Standard ISO 1133).

PVDF #3 is a PVDF #1 modified with 2.5% of carbon black in order torender it conductive.

Binder #1 is a mixture obtained by extruding a PVDF #1 (50% by mass) ofa copolymer of acrylic-imide type containing acid groups in itsstructure and displaying a flexural modulus of 4100 MPa (Standard ISO178) (15%) and a methyl methacrylate-butadiene-styrene (MBS) core-shelltype impact modifier (35%), on a twin-screw extruder.

Binder #2 is a mixture obtained by extruding a PVDF of fluidity 2 g/10min at 230° C. under 5 kg (Standard ISO 1133) (90%) and some of the samecopolymer of acrylic-imide type (10%), on a twin-screw extruder.

Binder #3 is similar to binder #2 but contains more acrylic-imide typecopolymer (20%)

The reground material of Example 6, placed between the outer layer of PAand the layer of binder #1, corresponds to the pipe of Example 1 whichhas been reground and extruded in the form of granules which may bereused directly as the starting material in a multi-layer structure.

Example 1 shows that the multilayer pipe is an excellent barrierstructure compared to a monolayer pipe made of PA. The pipe possesses anexcellent impact behaviour.

Example 2 shows, by comparison with Example 1, that the barrier propertyis provided by the PVDF+binder layers.

Example 3 shows that the use of a conducting PVDF has no effect on thebarrier and impact properties of the multilayer structure. The use of aconducting PVDF is useful if it is desired to obtain an antistatic fuelpipe.

Examples 4 and 5 show that the binder itself is a very good barriermaterial, and that a structure in which the barrier layer occupies amiddle position has a good cold impact resistance.

Example 6 shows that it is possible to introduce a layer of regroundmaterial between the layer of PA and the binder layer without disruptingthe impact and permeability performances.

Example 7 shows that an antistatic four-layer structure may be obtainedby means of the use of a conducting layer situated inside the main PVDFlayer.

Example 8 shows that a symmetrical 5-layer structure is also a goodsolution from the point of view of the impact and permeabilityproperties.

                  TABLE 3                                                         ______________________________________                                        Interfacial Adhesion in the pipes.                                                             Adhesion (g/cm) of the                                                        binder with                                                  Ex.   Structure of the Pipe                                                                          Outer Face                                                                              Inner Face                                   ______________________________________                                         9    Polyamide #2/Binder #1/                                                                        ++++      ++++                                               PVDF #1                                                                 10    Polyamide #2/Binder #3/                                                                        ++++      ++++                                               Polyamide #2                                                            ______________________________________                                    

Examples 9 and 10 show that the coextruded pipes have a perfect adhesionbetween the layers.

                  TABLE 3 bis                                                     ______________________________________                                        Interfacial Adhesion for films and plates.                                          Structure of     Adhesion (g/cm) of the                                       Three-layer      binder with                                            Ex.   Film             Outer Face                                                                              Inner Face                                   ______________________________________                                        11    Polyamide #1/Binder #1/                                                                        ++++      ++++                                               Fluorinated copolymer                                                         (200 μm/100 μm/200 μm)                                         ______________________________________                                    

The fluorinated copolymer is a copolymer of VF2 (90 mol %) and VF3 (10%)obtained by a suspension process. The films used in the test areobtained by extrusion through a suitable die. The three-layer film isobtained by pressing the films on a laboratory flat press at 230° C. for60 s.

Example 11 shows that the coextruded pipes have a perfect adhesionbetween the layers.

Table 4: Retention of Adhesion after Exposure to Aggressive Fluids.

The pipe tested is a Polyamide #2/Binder #1/PVDF #1 structure. Lengthsof the pipes are immersed for 1000 h at 60° C. in the aggressive fluidselected. The stripping test is carried out immediately after immersion.The stripping is initiated at the weakest interface.

These examples show that a very good adhesion persists under very severeconditions.

    ______________________________________                                        Test Aggressive Fluid                                                                              Adhesion                                                 ______________________________________                                        Diesel Fuel          ++++                                                     Solution containing 50% of Zinc                                                                    ++++                                                     chloride                                                                      Power Assisted Steering Fluid                                                                      ++++                                                     Motor Oil            ++++                                                     Calcium Chloride     ++++                                                     Test Fuel E15 (15% of ethanol in                                                                   +++                                                      fuel C)                                                                       Test Fuel M15 (15% of methanol in                                                                  +++                                                      fuel C)                                                                       Solution containing 50% of Ethylene                                                                ++                                                       glycol                                                                        Fuel C (50% toluene, 50%                                                                           ++                                                       isooctane)                                                                    Brake Fluid          ++                                                       ______________________________________                                    

I claim:
 1. An adhesion binder for a fluorinated polymer, which enablesthe fluorinated polymer to adhere to polymers with which it isincompatible, wherein the adhesion binder comprises a polymer Acomprising the moieties: ##STR5## in which R₁ and R₂, which may beidentical or different, represent H or a linear or branched alkyl havingfrom 1 to 20 carbon atoms; ##STR6## in which (i) R₄ and R₅, which may beidentical or different, represent H or a linear or branched alkyl having1 to 20 carbon atoms and (ii) R₃ represents H, an alkyl, cycloalkyl,aryl, alkaryl, aralkyl or a heterocycle; ##STR7## in which R₆ representsH or a linear or branched alkyl having from 1 to 20 carbon atoms; and##STR8## in which R₇ represents H or a linear or branched alkyl havingfrom 1 to 20 carbons and R₈ represents a linear or branched alkyl havingfrom 1 to 20 carbon atoms;and wherein it also comprises a second polymerin sufficient quantity to render it less rigid.
 2. The adhesion binderof claim 1, wherein said second polymer is selected from the groupconsisting of a fluorinated polymer, a modified fluorinated polymer, anda polymer which is compatible with polymer A.
 3. An adhesion binder fora fluorinated polymer, which enables the fluorinated polymer to adhereto an incompatible polymer selected from the group consisting ofpolyamides, copolyamides, polyamide alloys, and mixtures thereof,wherein the adhesion binder comprises a polymer A comprising themoieties: ##STR9## in which R₁ and R₂, which may be identical ordifferent, represent H or a linear or branched alkyl having from 1 to 20carbon atoms; ##STR10## in which (i) R₄ and R₅, which may be identicalor different, represent H or a linear or branched alkyl having 1 to 20carbon atoms and (ii) R₃ represents H, an alkyl, cycloalkyl, aryl,alkaryl, aralkyl or a heterocycle; ##STR11## in which R₆ represents H ora linear or branched alkyl having from 1 to 20 carbon atoms; and##STR12## in which R₇ represents H or a linear or branched alkyl havingfrom 1 to 20 carbons and R₈ represents a linear or branched alkyl havingfrom 1 to 20 carbon atoms;and wherein it further comprises a secondpolymer or polymer mixture in sufficient quantity to render it lessrigid.
 4. The adhesion binder of claim 3 wherein the fluorinated polymeris polyvinylidene fluoride (PVDF).
 5. The adhesion binder of claim 3wherein the second polymer comprises styrene/butadiene rubber andacrylic/styrene.
 6. The adhesion binder of claim 3 wherein the secondpolymer comprises the fluorinated polymer and a styrene/butadienerubber.
 7. The adhesion binder of claim 6 wherein the fluorinatedpolymer is polyvinylidene fluoride.
 8. The adhesion binder of claim 3wherein the second polymer comprises a methylmethacrylate-butadiene-styrene core-shell type impact modifier.
 9. Theadhesion binder of claim 3 wherein the polymer A is derived frompolymethyl methacrylate (PMMA).